In many industrial processes, there are high temperatures and adverse atmospheres. In this environment, materials may oxidize or corrode rapidly and/or creep. One example of such an environment is the process of thermal cracking for obtaining ethylene for polymer manufacturing. This requires great demands on corrosion resistance and high-temperature strength of the materials used. In this process, it is a goal to increase the service life of the material in order to decrease the number of maintenance shutdowns and expensive repairs. It is also a goal to raise the temperature in the manufacturing process in order to increase productivity.
One material used for high-temperature applications is ferritic iron-chromium-aluminum (FeCrAl) alloys. In many cases when a FeCrAl alloy is used as construction material, it has to be joined to another high-temperature material, which is often an austenitic stainless steel, such as a FeNiCr alloy. However, there are challenges joining these two materials by welding because of the differences in the material chemistry which causes difficulties formation of intermetallic phases, which will impair the mechanical properties of the weld.
WO 2014/204388 A1 discloses a filler for welding comprising (in % by weight): C: ≮0.036, Ni: 15.0-20.0, Cr: 15.0-22.0, Mn: 0.75-2.0, Zr: 0.1-1.45, Si: 0-1.5, Al: 0-2, N: <0.06 and a balance of Fe and inevitable impurities.
US 2006/163231 A1 discloses ferritic stainless steel welding wire consisting essentially of, by mass, 0.03% or less C, 3% or less Si, 3% or less Mn, 2% or less Ni, 11 to 20% Cr, 3% or less Mo, 1% or less Co, 2% or less Cu, 0.02 to 2.0% Al, 0.2 to 1.0% Ti, 0.02% or less O, 0.04% or less N, and at least one of Nb and Ta, the mass % thereof being eight times the total mass percent of said C and said N to 1.0 mass %, the balance being Fe and unavoidable impurities.
It is therefore of great importance to minimize and/or eliminate the formation of brittle intermediate phases formed during welding, especially when the objects to be joined are used in high temperature applications. It is also important to avoid the formation of a continuous film of brittle precipitations in the weld as this also will reduce the mechanical properties of the weld.
Thus, one aspect of the present disclosure is to provide a method of joining a FeCrAl alloy to FeNiCr alloy by welding in which at least one of the above problems is reduced or avoided.